Revert "fix(forms): apply unicode flag to pattern attribute when supported (#20819)" (#27375)

This reverts commit 3c34b8b4f1.

breaks google3 see http://cl/223526995

PR Close #27375

packages/forms/src/directives/validators.ts

@@ -379,11 +379,6 @@ export const PATTERN_VALIDATOR: any = {
  * as the regex to validate Control value against.  Follows pattern attribute
  * semantics; i.e. regex must match entire Control value.
  *
- * Note: if a string type attribute value is used, the regex will be applied with the
- * unicode flag on supported browsers. If a unicode-regex is passed, it might break on
- * unsupported browser. In this case, the user should be responsible to handle the
- * browser compatibility.
- *
  * @usageNotes
  * ### Example
  *

packages/forms/src/validators.ts

@@ -306,11 +306,7 @@ export class Validators {
 
       if (pattern.charAt(pattern.length - 1) !== '$') regexStr += '$';
 
-      if (RegExp.prototype.hasOwnProperty('unicode')) {
-        regex = new RegExp(regexStr, 'u');
-      } else {
       regex = new RegExp(regexStr);
-      }
     } else {
       regexStr = pattern.toString();
       regex = pattern;